Why is it that quality is lost when a picture is reduced in size?
Downsizing a picture is done by reducing the amount of pixels required to render a picture.
For instance if I take a pic in 'fine' jpg mode it takes the pic at a resolution of 300 DPI
(dots per inch) a very good picture rendering resolution. This means that I have over
90,000 dots per sq inch to render the image. Now when I go to display this image and I
want to keep the size down in order to not kill bandwidth for someone still using that 14.4K
modem, I will reduce it to 72 DPI or 5184 dpsi. That is roughly 5 percent of the original
resolution. Something has got to give and what gives is the detail in the image. No longer
do you have a five or ten pixel gradient along the edges since you lost that in the downsizing
and as a result have a one, maybe two pixel gradient in that detail. This is why you see the
'jaggies.' as they are called.
There is a lot more to it than this but this is the basics. Lower resolution images can be
enhanced to give the appearance of greater detail. Analog monitors will display 'nicer'
images in low resolution than digital monitors. In lower resolutions crappier monitors
actually will help as they will blur the pixels reducing the 'jaggies' by virtue of not being
able to render higher resolutions.
I notice on a lot of mine when I size them down using my HP Image Zone software that some of the lines look jagged and while the picture gets more vivid it also loses crisp lines.
But yet left alone they loo great. Take the one of my Romak 3 for example. I have that as my background on my PC and it looks 10x better than the resized image. Same goes for this shot:
On my end I see jagged lines on the top of the first rifle's bolt carrier and where the receiver meets the cover. Yet those aren't there when I have the image full size.
When it comes to digital imaging, image size matters to a point. Increasing image
size at some point gains very little in image quality as most displays can't do much
with the extra detail anyway.